badwords: check indented lines in source code, fix fallouts

- badwords.pl: add `-a` option to check all lines in source code files.
  Before this patch indented lines were skipped (to avoid Markdown code
  fences.)
- GHA/checksrc: use `-a` when verifying the source code.
- GHA/checksrc: disable `So` and `But` rules for source code.
- GHA/checksrc: add docs/examples to the verified sources.
- badwords.txt: delete 4 duplicates.
- badwords.txt: group and sort contractions.
- badwords.txt: allow ` url = `, `DIR`, `<file name`.

Closes #19536

src/tool_parsecfg.c

@@ -103,7 +103,7 @@ ParameterError parseconfig(const char *filename, int max_recursive)
 #if defined(_WIN32) && !defined(UNDER_CE)
     else {
       char *fullp;
-      /* check for .curlrc then _curlrc in the dir of the executable */
+      /* check for .curlrc then _curlrc in the directory of the executable */
       file = tool_execpath(".curlrc", &fullp);
       if(!file)
         file = tool_execpath("_curlrc", &fullp);